1. Field of the Invention
The present invention relates to a method of data transmission in wire or wireless network.
2. Description of the Related Art
Recently, the development of communication systems has enabled extensive transmission of moving image data which requires a relative wide communication band.
Moving image data is usually transmitted in real-time transport protocol (RTP) format, the RTP being a protocol designed for streaming real-time data such as voice and moving images.
When voice data or moving image data fails to be transmitted using RTP, for example, a technology called forward error correction (FEC) is used to recover the failed data in a receiving apparatus.
FEC is used to recover bit errors and lost packets that occur during data transmission, using error correction codes. A device for transmitting data generates redundant data by error correction coding of data to be transmitted, and transmits the redundant data with the data to be transmitted.
A device for receiving the data, when detecting an error and/or a lost packet in the received data, decodes the error correction codes using the data and the redundant data that are normally received, so that the packet sent in error is recovered.
Japanese Patent Application Laid-Open No. 2004-159042 discusses a method for recovering data packets that are lost in a communication path by a receiving apparatus based on redundant packets.
Not all of the lost packets, however, can be recovered by the redundant data.
For example, a plurality of data packets is generated using a single moving image frame, and a redundant packet (FEC packet) is generated for every four data packets that are successively transmitted. In transmission of the data packets and the FEC packets, if two or more packets out of the successive four data packets are lost, the lost packets cannot be recovered.
In most cases, such a loss of a plurality of packets in a short period of time cannot be recovered using redundant data.